1. Field of the Invention
The present invention relates to a semiconductor device and a method for fabricating the same. More particularly, the present invention relates to a semiconductor device having a thin film formed by atomic layer deposition and a method for fabricating the same.
2. Description of the Related Art
As semiconductor devices become more highly integrated, the fabrication of such semiconductor devices becomes increasingly difficult. In particular, a thin film used in the fabrication of semiconductor devices, for example, a silicon oxide layer or a silicon nitride layer, must be formed to have an excellent step coverage at a low temperature. In order to meet these demands, a thin film is formed using low pressure chemical vapor deposition (CVD).
FIG. 1 illustrates a schematic diagram of an apparatus for forming a thin film by conventional low pressure chemical vapor deposition. Referring to FIG. 1, a boat 3 on which a plurality of wafers 2 (semiconductor substrates) are mounted and a boat support 9 for supporting the boat 3 are installed in an inner tube 1 in the apparatus for forming a thin film by conventional low pressure chemical vapor deposition. The inner tube 1 is enclosed by an outer tube 5 which in turn is partially enclosed by a heater 7. A low pressure vacuum can be maintained inside the inner tube 1 and the outer tube 5 by a vacuum pump (not shown) connected to the lower right side of the inner tube 1. A reactive gas flows into the lower left side of the inner tube 1. At a temperature of 500˜800□C. and a pressure of several Torr a thin film is formed on the wafers 2. Then, an unreacted gas exhausts through the lower right side of the outer tube 5 by way of vacuum exhaustion. In FIG. 1, reference numeral 11 denotes an elevator for moving the boat 3 vertically, reference numerals 13 and 15 denote a vacuum manifold and a gas manifold, respectively, and reference numeral 17 denotes a vacuum flange.
However, the above mentioned apparatus for forming a thin film by low pressure chemical vapor deposition results in a high reaction temperature, and the thin film is formed on the plurality of wafers in a batch type, thereby increasing the thermal budget of the wafers.
Also, a process of consecutively forming a silicon oxide layer and a silicon nitride layer is widely used in fabricating the semiconductor device. The process of forming the silicon oxide layer and the silicon nitride layer must be separately performed in the apparatus for forming a thin film by conventional low pressure chemical vapor deposition, thereby causing an undesirable vacuum break.